This is the PDF of the

BIOS

March 12, 1998

1
 Introduction
In the past, DOS has accessed its mass storage devices using a BIOS provided INT 13 interface. This interface was designed
in the early 1980’s and upgraded in the late 1980’s. The maximum theoretical capacity of this API is 8.4 giga-bytes. This
INT 13 interface, now known as the legacy INT 13 interface, uses function numbers 1-15h and is Cylinder-Head-Sector
(CHS) oriented. An extended INT 13 interface has been created, the purpose of these Int 13h extensions is to:
Replace CHS addressing with Logical Block Addressing (LBA).
Remove the current requirement of using interrupt 41h/46h to point at the Fixed Disk Parameter Table information.
Give the BIOS better control over how this data is used.
Make location and configuration information available to operating systems that do not use the BIOS to access mass
storage devices.
Many BIOS, Option ROM, and OS vendors have already implemented the extensions defined in this document for ATA and
SCSI style devices. EDD 3.0 builds on EDD 1.1 to enable other mass storage technologies, such as 1394, Fibre Channel, and
USB.